Hardening gelatino silver halide emulsions with reaction products of halogenated triazines and hydrophilic organic colloids

ABSTRACT

A METHOD OF HARDENING PHOTOGRAPHIC LAYERS USING A NEW MACROMOLECULAR TYPE HARDENER, TO PROVIDE A GOOD WATER RESISTANCE AND YET A SUFFICIENT WATER ABSORPTION AND SWELLING THEERETO, WHICH IS PREPARED BY DISSOLVING A HALOGENATED TRIAZINE COMPOUND IN A LEAST QUANTITY OF A GOOD SOLVENT FOR BOTH SAID COMPOUND AND A HYDROPHILIC ORGANIC MACROMOLECULAR COLLOID BINDER TO MAKE THEM REACT IN AN AQUEOUS MEDIUM, THE PRECIPITATING AND SEPARATING THE REACTION PRODUCT WITH A LARGE QUANTITY OF A POOR SOLVENT FOR BOTH.

United States Patent US. Cl. 96111 3 Claims ABSTRACT OF THE DISCLOSURE Amethod of hardening photographic layers using a new macromolecular typehardener, to provide a good water resistance and yet a sufiicient waterabsorption and swelling thereto, which is prepared by dissolving ahalogenated triazine compound in a least quantity of a good solvent forboth said compound and a hydrophilic organic macromolecular colloidbinder to make them react in an aqueous medium, then precipitating andseparating the reaction product with a large quantity of a poor solventfor both.

BACKGROUND OF THE INVENTION Photographic materials are composed of aphotosensitive emulsion layer containing silver halide, which is themain constituent for photosensitiveness, and hydrophilic organicmacromolecular binders applied supplementarily thereon, for example theprotective layer, intermediate layer, underlayer and backing layer whosecomposition is almost the same as silver halide emulsion layer. Thusphotographic materials are composed of a layer or layers of hydrophilicfilm applied on one side or both sides of a water resistant support. Itis essential for these film layers, whether or not they arephotosensitive, that upon photographic treatment after exposure tolight, the developing solutions for photographic treatment should beallowed to sufiiciently penetrate and diffuse inthese layers. Since uponphotographic treatment not only the photosensitive layer but also thesesupplementary layers play an important role as well, all these filmlayers are also included hereinafter to photographic layers. In thesephotographic layers having no photosensitivity there is a hydrophilicbinder layer (called positive layer of the silver complex salt difiusiontransfer process or transfer layer) which contains fine heavy metallicnuclei for physical development. This layer, which is generally appliedseparately to the support independent of silver halide emulsion layer,plays an important role in image formation, which is the basis of thephotographic action. Therefore, such a transfer layer is also worthy ofbeing called a photographic layer.

For these photographic layers, binders whose main constituent is gelatinhave been widely used. In the past, natural substances such as starchand gum arabic were mainly used. In recent years, artifiicial'substancessuch as polyvinyl alcohol, polyacrylic acid, polyacrylamide, and variouswater soluble derivatives of cellulose, polyvinyl alcohol and starchhave widely come into use, solely or in mixture with gelatin. However,photographic layers comprising these water soluble binders are generallypoor in water resistance, and therefore swell in excess duringtreatments of developing, fixing and washing. As a result, troubles suchas reticulation, blister, and frilling are apt to cause. Therefore, itis usual to prevent the softening 3,717,467 Patented Feb. 20, 1973 ofthe film layers by adding a simple aldehyde such as formaline, acroleinand mucochloric acid or inorganic salt such as potash alum and chromiumalum to the film layers, or by treating them in a bath containing thesecompounds. In recent years, while severe developing treatment at hightemperature is required as a result of technical progress, requirementsare occurring for elevating the covering power of silver image with theuse of least amount of silver or increasing the developing rate. Forthese purposes, it is usual to mix Roentgen emulsion, etc. with a bindersuch as dextrin, gum arabic or a starch derivative which is lessresistant to water compared with gelatin. Various other binders are alsomixed as a plasticizer for the purpose of preventing the contraction ofthe film layer and increasing its softness. Also in this case, the waterresistance generally decreases. In order to reinforce this, strongerhardeners are required. While powerful hadeners comprising dialdehydecompounds, polyfunctional epoxy compounds or active vinyl compounds suchas vinyl sulfones and vinyl ketones are developed, macromolecularhardeners such as a copolymer of polyvinyl methyl ether with maleicanhydride, or of styrene with maleic anhydride, a monomaleic ester ofpolyvinyl alcohol or starch, or dialdehyde starch are also on themarket.

Macromolecular hardeners have in their long molecules many bondingpoints, where not only the molecules are crosslinked to each other butalso they are crosslinked to molecules of other binders mixed therein toform a network structure. Although a great amount of water iscoordinated and absorbed in this network, the film layer does notdissolve even when heated at a high temperature. This is acharacteristic of high polymer hardening agents. This offers a strikingcontrast with the char acteristic of low molecular hardeners which, whenthe more powerful they are, make the film layer the more horny,decreasing the water absorption and swelling property. In the case ofhigh polymer hardeners, they do not ditfuse or migrate from one layer toanother which are superposed upon each other. Therefore, it is a furtheradvantage of polymer hardeners that a given film layer could be hardenedto a desired extent without hardening other layers at all.

As powerful hardeners which have recently been developed, there arethose that have a nitrogen containing nucleus (such as s-triazinenucleus or pyrimidine nucleus) 7 having halogen atoms introduced thereinas reactive groups which react completely with binders at roomtemperature. A dyestuif of which molecule has such reactive groupsintroduced therein is a so-called reactive dyestulf, which has the mostpowerful dyeing power and is a compound containing a hydrophilic groupfor dyeing in an aqueous solution. For a hardener of this sort, it isnecessary, of course, to have water solubility in order to become ahardener for hydrophilic binder. Therefore, it has been believedhitherto that the hardener should be modified to the form of an alkalisalt as shown in the following Formula I (Japanese patent publicationNo. 17,112/

1 967), or it is necessary to introduce a carboxyl or sulfonic group asshown in the Formula I-Ia or IIb (Japanese patent publication No.16,9Q8/ 1964). (-In fact all the reactive dyestulfs have the latterform.)

or =N N; ;C-NHCHzCOOH C-N (31 Ha o1 j s no C-NH-Q-SOaH SUMMARY OF THEINVENTION A compound of the general formula or Na; R-C O-NHNHC/ 1;

wherein X is N: or CH R is H, CH or C H preferably or N--& CH;CONHNHC%\N 2 (Racetamino) phenylamine-4,6-dlcl1loro-1,3,5triazine is made toreact in water with a Water soluble organic macromolecular colloidalbinder for photographic use. Said compound is dissolved with a leastpossible amount of a Water miscible organic solvent which is acomparatively good solvent for both said compound and, said binder.After they have reacted homogeneously a great amount of a water miscibleorganic solvent which is com-- paratively poor solvent for both is addedto precipitate the reaction product. The reaction product is separatedand added to the main protective colloidal binders to constitute thephotographic layer as a hardener. Said good solvents include formamide,dimethylformamide, dimethylformarnide, dimethylsulfoxide andtetrahydrofuran, and said poor solvents include methanol, ethanol;n-propanol, iso-propanol, butanol, acetone, and methyl ethyl ketone.

DETAILED DESCRIPTION In consideration of all those facts described inBackground of the Invention, the inventors have come to an idea thatwhen a compoundwhich is easier to synthesize 4 could be achieved, eventhough these compounds are not dissolved in Water.

Compounds having the following general formula were proposed for thispurpose.

wherein X is -N= or --C; and R is H or an alkyl group having up to abouttwo carbon atoms, namely CH or CZH5.

These compounds were attempted to be dissolved in such a solvent asmentioned above which is well miscible with water, and to be addeddirectly to the solution for a photographic layer-of silver halideemulsion containing a binder solution or binder. These compounds,however, when used actually, dissolve at most to an extent of only 0.1%in an ordinary water miscible solvent such as alcohol or acetone. Andwhen a fairly large amount of these compounds are added to the solutionof hydrophilic organic high polymer such as gelatin or polyvinylalcohol, which is to form the binder of the photographic layer, thehydrophilic binder is preciiptated and coagulated by these compounds,which act as a sort of precipitating agent. In general, necessary amountof a hardener to be added to gelatin is at least about 0.5 to 1% basedon the weight of the dry weight of gelatin. On the other hand, thehardener dissolves in alcohol only to an extent of 0.1%. Accordingly, ifsilver halide emulsion, whose binder is for example gelatin, is desiredto be hardened by this method, necessary amount of the hardener is 0.05to 0.1 g. for ml. of the emulsion containing 10% of gelatin. Thisnecessitates to add 50 to 100 ml. of alcohol, thus allowing toprecipitate and separate out the emulsion at once. Therefore, it isrequired to added a more concentrrated solution of the hardenerdissolved in an especially powderful solvent such as formamide,dimethylformamide, or tetrahydrofuran. When a 2% solution of thehardener dissolved in such a solvent is used in the'above example,necessary amount of thesolvent is only 2.5 to 5 ml. Further, thesesolvents are good solvents for high polymers in general and also forgelatin, starch and polyvinyl alcohol, and naturally do not precipitatethem. Thus, there is no problem in this point. 0n the contrary, however,even a small amount of them causes the physical properties (settingpoint, melting point, tenacity of the film, viscosity of the liquid,etc.) or hydrophilic binders such'as gelatin to be markedly injured,thus leading to troubles in the applying and drying operation of thesolution. Accordingly, it would be better, if'possible, to avoid directiapplying of these powerful solvents to the photographic ayer.

Now the inventors, after repeating many experiments, have succeeded in:making it possible to add to the photographic layer the hardener that ismade soluble in water to a desired extent using a proper combination oftwo orgarn'c solvents miscible with water, avoiding their unfavorableeifects. If these powerful solvents are used, it is easy to add anecessary amount of hardener to the binder. Thus, the hardener is addedto the solution'of a hydrophilic' binder such as gelatin, polyvinylalcohol, starch, etc. together with such a solvent. In an appro priatestep of 'the reaction. (Theoretically, it is obvious that the degree inwhich one of the two halogen atoms of triazineor pyrimidine nucleus hasreacted issuitable.) A great amount of a solvent such as methanol,ethanol, n-propanol, i'sopr'opanol," acetone, or methyl ethyl ketonewhich is miscible with water but is 'a poor solvent for the binderlisadded to precipitate the binder which has been made to react. The motherli uid is removed, the

precipitate is washed with alcohol, the precipitate is dissolved inwater and the dissolved precipitate is precipitated again. By theseoperations, the powerful solvent such as formamide, unreacted hardener,hydrogen halide produced as a by-product is washed away. Thus, thedesired binder combined with the hardener is separated in a purifiedform as a hardener of the macromolecular type. Even if about 0.5 to 10%of the above-mentioned hardener based on the dry weight of the binderare made to react and combined, the reaction product does not usuallylose the characteristic water solubility of the binder. Therefore, thereaction product precipitated with alcohol or acetone and dried may bedissolved in water again to use. But usually this is dissolved again inwater without being dried in this step, and is used for hardening ofphotographic layer as an aqueous solution containing neither alcohol northe powerful solvent such as formamide which is unfavorable to thephysical properties of the coated layers. Thus this hardener of the highpolymer type can be used as a part of the binder which forms thephotographic layer. If, for example gelatin containing 5% of hardener isobtained, and is substituted for to 20% of the whole binder, thepercentage of the hardener in the whole binder is equivalent to 0.5 to1% of the hardener added to the whole binder. Thus a photographic layerhaving a sufiicient hardening property and yet having excellent waterabsorption is obtained. As a result of overall consideration of thedifficulty of synthesis, yield, cost, stability of the resultingsubstance, solubility in alcohol, and reactivity in these cases, it hasbeen confirmed that2(pacetamine)-phenylamine-4,6-dichloro-1,3,5-triazine having thefollowing formula is the most suitable for this purpose.

(Ill N-O C at (This is the case wherein X is N=, R is CH in thepreviously mentioned general formula.) This substance is synthesized innearly theoretical yield by a known method (for example J. Phot. Sci. 11(1963), p. 340). The purified product is a purely white crystal having amelting point of 236 to 237 C. (decomposition) and is much more stablethan the p-formyl compound. (The case where R=H in the general formula.)In the above literature, it is described that the solubility in ethanolis about 2.8% at a high temperature and about 1.2% at a low temperature,However, this would be an error. According to the inventorsmeasurements, the solubility in ethanol or methanol was both less thanO.-1%, and 2 to 3% in formamide, dimethylformamide, etc. Since thissubstance has dichlorotriazine group, it naturally reacts and combinesin a neutral or alkaline condition with various substances having 'NH,NH or OH groups such as gelatin, polyacrylamide, polyvinyl alcohol orcellulose, etc., while liberating hydrochloric acid. Usually onechlorine atom reacts at first, and two chlorine atoms do not react inwater if not in a severe condition. It is aimed in this invention whenthe dried film layer is cured, two chlorine atoms react to formcrosslinkage between the molecules. I

Among hydrophilic binders having reactive groups such as NH, NH OH,etc., gelatin is most widely used. Besides gelatin, the followingsubstances may be used: casein, polyacrylamide, poly-alanin, a copolymerof -a1anin with acrylamide, polyethylene iniide, polyvinylamine,polyvinyl alcohol, vinyl polymers, copolymerized with these polymers, orderivatives of these compounds, etc. Polyvinyl alcohol is well known asa substitute for gelatin, and reacts and combines with thisdichloro-s-triazine compound like cellulose. But it is difficult to mixpolyvinyl alcohol itself with gelatin. A derivative of this compound ofwhich a part of OH groups is changed to monoester of a dibasic acid maybe mixed with gelatin easily. A copolymer of vinyl ethyl ether withmaleic anhydride, or a copolymer of styrol with maleic anhydride doesnot react but becomes more reactive when they are changed to half-amidewith the use of ammonia or an amine group, and can be used for thispurpose. Accordingly, every binder mentioned above should also beconsidered as a kind of a water soluble organic high polymer colloidalbinder capable of reacting and combining with dichloro-s-triazinenucleus.

EXAMPLES Example 1 Five grams of 2(p acctamino)phenylamino-4,6-dichloro-l,3,5-triazine, 250 g. of dimethylformamide andN-NaOH solution were added dropwise under stirring at 40 C. to a gelatinsolution comprising 100 g. of gelatin for photographic use and 1900 ml,of distilled water, the NaOH solution being added so that the pH of thegelatin solution is maintained at a value between 7 and 8. Thetemperature was maintained between 40 to 45 C. After the whole solutionis mixed, it is maintained at the same temperature for one hour toperform a reaction thoroughly. Then, while cooling the whole solution,about 4 liters of acetone were added and the reaction product wasprecipitated. The supernatant was removed, and the precipitate waswashed with one liter of ethanol. The mother liquid was removed, oneliter of distilled water was added, and the water was warmed to dissolvethe precipitate. After cooling, two liters of acetone were added toprecipitate again. Then, after distilled water was added to make up toone liter and the whole solution was warmed, it was again cooled to set.The coagulum was shredded into small noodles. The resulting jelly wasused without being dried. During such operation, the loss of gelatin isusually about 15 to 20%. Therefore, 120 g. of the jelly are consideredto correspond to 10 g. of gelatin and 0.5 g. of the hardener. Uponadding the jelly to the emulsion etc., this Was taken into account.

Measurement of the hardening power was conducted as follows:

As shown in the following table, gradually increasing amounts of thejelly were added to 10% gelatin solution and were dissolved. Theresulting solutions were applied respectively on glass plates to form anequal thickness and dried. After curing for 24 hours, the glass plateswere warmed gradually in water and in an ordinary developing solution.The temperatures at which the coated layers on the plates soften anddissolve were measured and deter mined as the melting points. As shownin the table, it was found that almost complete hardening was achievedwith about 1% of the hardener. Even with about 0.5%, hardeningsufiicient for practical use was attained.

A. B C D E Composition of the solution applied (g.):

Resulting jelly 0 3. 0 6 12 24 10% gelatin solution 50 47. 5 45 40 30 Wor 50 49. 5 49 48 46 Hardener/gelatin 0 0. 25 0. 5 1.0 2.0 Melting pointof dried film 0.):

In water 32 32 61 100 100 In developing solution... 32 39 66 Example 2According to the method of D. Klinke (Z. wiss. Pht. 57 (1963), p. 154),maleic monoester of polyvinyl alcohol of substitution ratio of about 50%(half of OH groups of polyvinyl alcohol being substituted by vinylmaleic groups) was easily synthesized with g. of polyvinyl alcohol and300 g. of maleic anhydride in 200 g. of glacial acetic acid in thepresence of 200 g. of sodium acetate as the catalyst. The yield was g.and a part of the carboxylic acid was found to have changed to itssodium salt. In the following there will be shown an example in whichthe abovementioned reaction product was used. (Similar results wereobtained with reaction products of ditierent degree of substitution.)

Fifth grams of the above-mentioned maleic monoester of polyvinyl alcoholwere dissolved in one liter of distilled water. To this solution 2 g. of2(p-acetaminoJ-phenylamino-4, 6-dichloro-l,3,5-triazine and 100 ml. offormamide were added dropwise at a temperature of 40 to 50 C., whileregulating the pH of the solution at a value of from 7 to 8 with N-NaOHsolution. After the addition was finished, the same temperature wasmaintained for two further hours. Thereafter, the solution was pouredinto 6 liters of cold methanol to form a precipitate. The supernatantwas removed and the precipitate was washed twice with a small amount ofmethanol. Then the precipitate was dissolved in 500 ml. of distilledwater and was precipitated again with 3 liters of methanol. After beingwashed with methanol, the precipitate was dissolved in distilled waterto make up to 500 ml., thus obtaining about a 10% solution of thehardener of this invention.

A concentrated emulsion produced by forming a precipitate from a highsensitive bromide emulsion according to an ordinary method usingphthalic monoester of polyvinyl alcohol was prepared. (This method ofprecipitation Was filed for another Japanese patent application, andtherefore a brief explanation is made here.) One liter of a 10% solution(pH 6.5) of polyvinyl monophthalate (the substitution ratio being about53%) was added to 3.5 liters of an emulsion prepared from 100 g. ofsilver halide and 300 g. of gelatin, and at pH 3 a concentrated emulsionwas obtained as a precipitate in the form of mass. This was washed twicewith 1% acetic acid, and 1.6 kg. of a concentrated emulsion wasobtained. Thus 160 g. of this concentrated emulsion contains 30 g. ofgelatin and 10 g. of polyvinyl alcohol monophthalate, and thisconstitutes a part of the final binder.

Now color photographic paper for silver dye bleaching method wasprepared as follows: At first 100 g. of the hardener solution of thisinvention was added to 160 g. of the above concentrated emulsion. Then,optical sensitizing dyestuffs for red and blue were added respectivelyto the emulsions in order to form cyan and magenta layers. Further,emulsions added with about 3 g. of Direct Blue (CI 24410), and DiamineRose (CI 15080), and about 6 g. of Brilliant Yellow (CI 124890) wererespectively prepared. To these emulsions were added the ordinaryadditives before applying including stabilizers for each emulsion andsaponin, and the total weight of the liquid was made up to 600 g. withwater.

On the other hand, as the solution for the intermediate layer andprotective layer 30 g. of gelatin and 10 g. of hydroxypropyl starch weredissolved in water together with 100 g. of a 10% aqueous solution of thehardener of this invention, and additives of nearly the same compositionas in the emulsion were added. The solution was made up to 600 g. On thesurface of so-called RC paper which right surface and reverse surfaceare respectively coated with pigment-filled polyethylene added withtitanium di-oxide and polyethylene resin-first 30 g./m. of theabove-mentioned red sensitive cyan color emulsion was applied and 20g./m. of an intermediate layer was applied thereon; then the greensensitive magenta color emulsion layer and other intermediate layer wereapplied similarly; finally the blue violet sensitive yellow coloremulsion layer and the protective layer were applied, and the resultingpaper was dried. Thus, photographic paper suitable for obtainingenlarged color positive images from color slides by the so-called silverdye bleaching method was prepared.

In this case, for each layer, the ratio of polyvinyl alcohol monomaleateto the whole binder was 20% and the ratio of the monochloro-s-triazinehardener added thereto was 1% On the other hand, the hydrophilic binderexcept gelatin goes up to 40% based on the weight of the total binder.Therefore although this photographic layer has good water absorption andswelling property and low development inhibiting power, the wholehardening property is excellent and completely withstands the treatmentof strong hydrochloric acid bleaching solution of the silver dyebleaching method. Moreover, since this hardener acts as a good mordantfor acid dyes there was no necessity for further mordant treatment.

We claim:

1. A method of hardening a photographic layer comprising admixing anaqueous solution of a reaction product of (1) a compound of the formulawherein X is a moiety selected from the group consisting of ---N: andCH= and R is selected from the group consisting of hydrogen, methyl andethyl with (2) a hydrophilic colloid binder selected from the groupconsisting of gelatin, starch, poly(vinyl alcohol), gum arabic,polyacrylic acid, polyacrylamide, polyvinyl methyl ether-maleicanhydride, styrene-maleic anhydride copolymers, dextrin, casein,poly-fi-alanin, a copolymer of ,B-alanin and ncrylamide and polyvinylamine into a gelatino-silver halide emulsion constituting thephotographic layer, and wherein the aqueous solution of the reactionproduct is prepared by (a) dissolving a hardening amount of saidcompound in a least amount of a water miscible good solvent for bothcomponents selected from the group consisting of formamide,dimethylformamide, dimethylsulfoxide and tetrahydrofuran,

(b) admixing the resulting solution into an aqueous solution of saidhydrophilic colloid binder and causing said compound to react with saidhydrophilic colloid binders in a homogeneous state,

(0) precipitating the reaction product with a large amount of a watermiscible poor solvent for both components selected from the groupconsisting of methanol, ethanol, 11- propanol, iso-propanol, butanol,acetone, and methyl ethyl ketone,

(d) Washing with water and (e) dissolving said reaction product in anaqueous medium.

2. The method of claim 1 wherein said hardener is 2(p-acetamino)-phenylamino-4,6-dichloro-1,3,5-triazine.

3. A photographic element comprising a support having thereon at leastone gelatino-silver halide emulsion layer containing an aqueous solutionof a reaction product of (l) a compound of the formula wherein X is amoiety selected from the group consisting of N: and CH= and R isselected from the group consisting of hydrogen, methyl and ethyl with(2) a hydrophilic colloid binder selected from the group consisting ofgelatin, starch, poly(vinyl alcohol), gum arabic, polyacrylic acid,polyacrylamide, polyvinyl methyl ether-maleic anhydride, styrene-maleicanhydride copolymers, dextrin, casein, poly-B-alanin, a copolymer offi-alanin and acrylamide and polyvinyl amine wherein the aqueoussolution of the reaction product i prepared by (a) dissolving ahardening amount of said compound in a least amount of a water misciblegood solvent for both components selected from the group consisting offormamide, dimethylformamide, dimethylsulfoxide and tetrahydrofuran,

(b) admixing the resulting solution into an aqueous solution of saidhydrophilic colloid binder and causing said compound to react With saidhydrophilic colloid binders in a homogeneous state,

(c) precipitating the reaction product with a large amount of a Watermiscible poor solvent for both components selected from the groupconsisting of methanol, ethanol, n-

10 propanol, iso-propanol, butanol, acetone, methyl ethyl ketone, (d)washing with water and (e) dissolving said reaction product in anaqueous medium, and wherein said reaction product is present in anamount sufiicient to cause hardening of said gelatino-silver halideemulsion layer.

References Cited J. TRAVIS BROWN, Primary Examiner W. H. LOUIE, JR.,Assistant Examiner US. Cl. X.R.

